Uprights are used to hold a net in position for athletic or recreational sporting activities, such as volleyball, tennis, and badminton. Many sporting facilities are constructed with a court or a playing surface that is multifunctional. For instance, the playing surface may, on occasion, be a basketball court, at other times the court may be setup for badminton, tennis, or volleyball. To support a multifunctional role, the playing surface may have a plurality of sleeves or recesses installed in the playing surface. One end of the upright is typically inserted into the sleeve. The sleeves permit the upright to be installed and removed, allowing the playing surface to be converted from facilitating one sport to another sport. For badminton, tennis, and volleyball, two uprights are generally required to provide support for the net to be strung tautly between the uprights.
Most sporting regulations require that the net be taut between the uprights. By pulling the net taut, the load on the upright increases, causing the upright to flex in the direction of the net. In most regulation sports, only minimal flexing of the upright is permitted. As the upright length increases it must be more resistant to flexing. In other words, the upright must be more rigid. This is particularly true for volleyball.
In use, in addition to holding the net in position, the uprights must be able to withstand impact of a ball on the net, and the impact of one or more players into the net or pole. The latter of the two impacts can amount to significant forces on the upright due to the momentous forces produced by a moving body.
Some uprights have telescopic designs. Two tubes, one having a smaller diameter, are constructed so that one extends from and slides within another. Once the desired net playing height is set, the two tubes are locked into position relative to each other. Telescoping adjustable height uprights serve different classifications of players. For example, a youth league may require a lower net playing height than an adult league, which may have different net playing heights for women than for men. This telescoping design permits adjustment of the net to meet the net playing height requirements for multiple leagues of varying skill levels.
In addition to having flexible height setup, the upright should be easy to handle for setup and removal. The weight of the upright may influence the ease with which the upright is installed and removed from the sleeve. Obviously, as the upright weight increases, handling the upright during installation and removal becomes increasingly more difficult and, possibly, dangerous. Not only is bodily injury an issue for heavy uprights, damage to the playing surface may also occur. Therefore, light uprights are more desirable because they are easier and safer to install and remove. Unfortunately, light uprights generally lack the durability and rigidity desired, that is, light uprights flex more and are more likely to fail under reasonable playing conditions.
Like with other sporting goods, advanced materials have allowed some reconciliation between the competing design requirements. Composites are one type of advanced material. Composites offer the advantage of having lower weight with greater rigidity, making them an attractive alternative to multi-material components. Fiber reinforced composites consist of a plurality of fibers of one material that are bound in a matrix of resin or another organic material. The reinforcing fibers tend improve the rigidity of the matrix while the matrix distributes the load among the fibers. One of the drawbacks with fiber reinforced composites is that many of the fibers found in composites are susceptible to flaws or defects on their surfaces. These defects may cause the composite to fail or fracture when placed under a load. Moreover, composites are less durable than their multi-material counterparts mainly due to defects caused by abrasion. In the case of the upright, abrasion from installation, setup, and removal, may cause a reduction in the rigidity and strength of the composite.
There remains an unfulfilled need for a composite locking upright that is light in weight but does not sacrifice durability and useable life to attain its light weight. Additionally, there remains an unfulfilled need to provide a composite locking upright which is rigid while being cost effective.